Key Indicators of Water Quality and Mineral Content

Electrical Conductivity in Water

Electrical Conductivity: Pure water is a poor conductor of electricity. It is the impurities in the water, such as dissolved salts, which allow water to conduct electricity. It is found that a great indicator of the total level of impurities in fresh water is its electrical conductivity—the efficiency with which water transmits electrical current.

The more impurities it contains, the higher the electrical conductivity. For domestic purposes, the preferred water has a total dissolved solids (TDS) content of less than 500 ppm, or a conductivity below approximately 750 microSiemens (ohm⁻¹).

Water Alkalinity and pH Resistance

Alkalinity: Alkalinity is the measure of water's resistance to reductions in pH when acids are added. These acid additions generally come from rain or snow. Alkalinity is generated as water dissolves rocks containing calcium carbonate, such as calcite or limestone.

When a lake or stream has very low alkalinity, usually below 100 mg/l, a large inflow of acid from a rainstorm or melting snow can quickly (at least temporarily) consume all of the alkalinity and cause the water pH to drop to dangerous levels.

Nitrates and Nutrient Levels

Nitrates: Plants in both saltwater and freshwater require three major nutrients for growth: carbon, nitrogen, and phosphorus. In fact, most tend to use these three nutrients in the same proportion and cannot grow if the quantity of any of them is insufficient.

Carbon is abundant in the air as carbon dioxide, which dissolves in water; therefore, a lack of nitrogen or phosphorus generally limits the growth of aquatic plants. Nitrogen exists in multiple forms within water bodies; of these, nitrates are usually the most important. Nitrite is normally found in sub-toxic waters (with low levels of dissolved oxygen). When an excessive amount of a limiting nutrient, such as nitrogen, is added to a lake or stream, the water is enriched and promotes increased growth of algae and other plants. This process is called water eutrophication.

The excess of plants growing as a result of this process can cause significant problems. Most natural waters have nitrate levels lower than 1 mg/l of nitrate-nitrogen, but concentrations above 10 mg/l are found in some areas.

Understanding Water Hardness

Hardness: Hard water is water that contains a high level of minerals and has varying amounts of compounds, including magnesium and calcium salts. These are the primary causes of water hardness, and the hardness level is directly proportional to the concentration of these salts.

Hard water is characterized by the following:

• It does not produce foam easily with soap.
• It can sometimes discolor clothes or make it impossible to wash them properly.
• It forms a hard crust (scale) in pots and on taps.
• It can sometimes have an unpleasant taste.

Hard water contains ions that form precipitates with soap or upon boiling. Hard water can be softened using appropriate methods, such as softening with ion exchange resins or specific magnetic systems.